Recently, there has been an increased public awareness and professional concern over the release of mercury from dental amalgam. Although it is generally believed that the level of mercury emitted from amalgam in situ is low, there is little information available on the quantity, mechanism of release or biological effect of this low level of mercury. The goal of this research proposal is to systematically investigate the quantity, rate and mechanisms of mercury release from dental amalgams and their constituent phases by evaporation, sublimation and dissolution into the oral environment. To accomplish this goal, four experimental techniques will be employed: 1) The rate and quantity of mercury released from three different amalgams and their constituent phases during aging at several temperatures and time periods will be determined by weight-loss measurements; 2) The effect of age, environment and surface condition on the rate and quantity of mercury released from amalgams and their constituent phases will be determined using a clinically used mercury vapor analyzer; 3) Scanning electron microscopy and x-ray energy dispersive analysis will be employed to identify the microstructural changes and solid state reactions that occur in amalgams and their constituent phases during aging at various temperatures and time periods. These changes will then be related to the evolution of mercury to propose sites and mechanisms for the evaporation or sublimation of mercury from amalgam; 4) The dissolution of mercury from different polished and unpolished amalgams, amalgam phases and galvanic couples of specific amalgam phases will be determined with atomic absorption spectrophotometry. It is believed that this study will provide scientific evidence to aid in determining the ultimate exposure of the patient and dental personnel to mercury from present and future dental amalgams.